South Korean President Moon Jae In said Seoul and Washington agree that the crisis over the North’s nuclear programme should “absolutely be solved peacefully,” and that no US military action on the Korean peninsula could be taken without Seoul’s consent.

Mouthy US President Donald Trump had boasted on Friday that his military was “locked and loaded.”

But Mr Moon said: “Our government will put everything on the line to prevent another war on the Korean peninsula,” Mr Moon said. “The [South Korean] government and the US government don’t have a different position on this.”

And North Korean leader Kim Jong Un said he would watch the “foolish and stupid conduct of the Yankees” before deciding to carry out his threat to fire four ballistic missiles into the sea near US colony Guam.

The test, which Kim III said was ready, was planned after the latest biannual US-South Korea war games near the 38th parallel.

Mr Kim said the US must “make a proper option first and show it through action, as it committed provocations after introducing huge nuclear strategic equipment into the vicinity of the peninsula.”

The US “should stop arrogant provocations at once,” he added.

A Foreign Ministry spokesman denied Pyongyang was negotiating with Washington over the release of three jailed US citizens, saying: “The issue on detained Americans is not an object to discuss in view of the present atmosphere of DPRK-US relations.”

US military chief of staff General Joseph Dunford met South Korean generals and ministers in Seoul on Monday before flying to Beijing for talks with his Chinese counterpart yesterday.